本文選題：電離層空洞 + 邊界層過程　； 參考：《中國科學(xué)技術(shù)大學(xué)》2015年博士論文

【摘要】：電離層是地球大氣的一個電離區(qū)域,其存在對大氣電學(xué)和地球磁層的形成起著重要作用。電離層活動異常會對空間及地面技術(shù)系統(tǒng)造成嚴重危害,尤其是隨著人類活動范圍的進一步擴大,無線電通訊、衛(wèi)星導(dǎo)航、航天器飛行、空間天氣預(yù)報等活動都會受到電離層變化的影響。因此開展人工影響電離層空間天氣的研究具有重要意義,而化學(xué)物質(zhì)釋放擾動電離層形成電離層空洞就是一種可行的人工影響空間天氣的方法。電離層空洞可以影響無線電波的傳播、高功率微波加熱電離層的效率等一系列空間活動；同時在基礎(chǔ)研究方面也提出了許多亟待解決的問題,例如電離層空洞邊界層存在著從離子頻率到低混雜頻率的等離子體不穩(wěn)定性,而這些不穩(wěn)定性的產(chǎn)生與增長是電離層空洞的演化過程必須考慮的因素。因此,化學(xué)物質(zhì)釋放形成電離層空洞的研究是一個兼具國防安全和基礎(chǔ)等離子體物理前沿的研究課題。 世界各國科學(xué)家在過去幾十年進行了大量化學(xué)物質(zhì)主動釋放制造電離層空洞空間實驗和數(shù)值模擬研究。由于空間主動實驗的主要手段依賴于相干散射雷達、非相干散射雷達、全天光譜儀以及一些地基、箭載和星載設(shè)備,這些對設(shè)備磁流體大尺度的物理問題研究很有優(yōu)勢。但是設(shè)備自身時間空間分辨率的限制,對電子離子混雜不穩(wěn)定性這樣的動理學(xué)尺度的不穩(wěn)定性過程目前并沒有很好的研究結(jié)果。 我們在實驗室等離子體中研究了化學(xué)物質(zhì)主動釋放形成電離層空洞邊界層的非線性演化,首先驗證了實驗室環(huán)境下研究電離層空洞的可行性。由于空氣輝光放電的組分和化學(xué)過程都接近于真實電離層環(huán)境,本論文采用空氣輝光放電等離子體來模擬電離層環(huán)境。在背景等離子體形成之后,我們釋放SF6、CC12F2和C02進入等離子體來形成模擬電離層空洞。實驗采用微波干涉法和光譜法來研究模擬電離層空洞的演化,觀察到了密度梯度隨著等離子體氣壓和釋放比例的演化,發(fā)現(xiàn)不同化學(xué)物質(zhì)釋放造成的密度梯度與空間主動實驗的觀測結(jié)果相一致。同時,我們還發(fā)現(xiàn)負離子中間產(chǎn)物(NI)物質(zhì)比正離子中間產(chǎn)物(PI)物質(zhì)降低電子密度效果明顯；并且NI物質(zhì)形成電離層空洞需要的時間較PI物質(zhì)更短。這些結(jié)果與相應(yīng)的空間主動實驗觀測結(jié)果一致。同時,我們還觀察到了SF6釋放造成777.4m的氣輝增強和C02釋放造成的630nm的氣輝增強,這與全天光譜儀觀測的結(jié)果一致。證明實驗室等離子發(fā)生著和主動空間實驗相同的過程,從而驗證了我們研究方法的可行性。 在此基礎(chǔ)上我們發(fā)展了一種在實驗室環(huán)境下研究電離層空洞產(chǎn)生與演化的方法,即通過無量綱參量定標(biāo)的方法在實驗室中產(chǎn)生ωpe/ωce、β值等一系列無量綱參量與真實空間環(huán)境相同或接近的等離子體；基于此我們可以在實驗室實現(xiàn)和空間等離子體相同的物理過程。由于實驗室環(huán)境下,可通過控制實驗參數(shù)實現(xiàn)對電離層空洞邊界層的物理問題進行詳細研究。同時實驗室等離子體診斷的時空分辨率相比空間觀測都有較大優(yōu)勢,因此實驗室環(huán)境通過定標(biāo)方法可以精確研究電離層空洞邊界層演化等微觀物理問題。 我們通過該方法在實驗室研究了電離層空洞邊界層的非線性演化過程,得到了邊界層等離子體電子密度和等離子體電勢的演化過程。我們觀測到邊界層上存在巨大的密度梯度Vn。和等離子體電勢中f上升,發(fā)現(xiàn)在邊界層電子密度梯度Vn。為等離子體電位漲落提供自由能。由于等離子體懸浮電位中f的變化會導(dǎo)致非均勻電場E(r)的產(chǎn)生,進一步在邊界層激發(fā)剪切E×B流的產(chǎn)生。剪切流會驅(qū)動一系列從離子頻率到混雜頻率的等離子體不穩(wěn)定性。通過對電子密度和等離子體電位的漲落做數(shù)字信號譜分析,我們發(fā)現(xiàn)懸浮電位漲落中存在一個低混雜頻率范圍內(nèi)波結(jié)構(gòu)。通過對該結(jié)構(gòu)進行互功率譜分析和雙譜分析,我們證實了該結(jié)構(gòu)為剪切流驅(qū)動的電子離子混雜不穩(wěn)定性(Electron-Ion Hybrid Instability)形成的的渦狀相干結(jié)構(gòu)。邊界層電子離子混雜不穩(wěn)定性的增長以及渦狀相干結(jié)構(gòu)的形成對電離層空洞的非線性演化起著重要作用。例如,邊界層密度不規(guī)則體的形成就與電子離子混雜不穩(wěn)定性相關(guān)。我們在實驗室發(fā)現(xiàn)了該結(jié)構(gòu)的存在對解釋諸多空間主動實驗的觀測結(jié)果具有重要意義。 我們還研究了電離層空洞邊界層出現(xiàn)的電磁漲落。磁探針的信號顯示,邊界層上存在較強的電磁漲落。該漲落具有BT、BZ和Bθ分量,并且θ的分量遠遠大于其他分量。數(shù)字信號譜分析顯示磁場漲落中存在一個低混雜頻率的結(jié)構(gòu)。經(jīng)過對信號進一步進行互相關(guān)分析,我們發(fā)現(xiàn)這是右旋極化的哨聲模式。并且通過靜電電子離子混雜模式和電磁模式的頻率對比,我們判斷該哨聲模式來源于靜電電子離子混雜模式的非線性散射,這是首次給出從靜電頻率向電磁頻率轉(zhuǎn)化的實驗證據(jù)。 總之,我們在實驗室環(huán)境下研究了化學(xué)主動釋放形成的電離層空洞邊界層的演化過程。通過采用無量綱參量定標(biāo)的方法,我們研究了該區(qū)域的靜電漲落和電磁漲落；發(fā)現(xiàn)了靜電電子離子混雜模式以及其電磁波段哨聲模式存在的證據(jù),同時間接證明了邊界層靜電電子離子混雜模式可以經(jīng)過非線性散射轉(zhuǎn)化為電磁哨聲模式。這些靜電以及電磁漲落對邊界層的演化過程動力學(xué)行為起著重要作用。由于實驗室研究能夠?qū)υS多空間觀測不到的微觀物理能進行詳細研究,因此它能與目前電離層空洞的主要兩種研究方法(空間主動實驗和數(shù)值模擬)形成了一個很好互補效果,為國家即將開展的主動空間實驗研究積累經(jīng)驗。
[Abstract]:The ionosphere is an ionizing region of the earth's atmosphere. Its existence plays an important role in the formation of atmospheric electricity and the formation of the earth's magnetosphere. The abnormal ionospheric activity will cause serious harm to space and ground technology systems, especially with the further expansion of human activities, radio communication, satellite navigation, spacecraft flight, space weather preconditioning. Newspapers and other activities are affected by the ionosphere change. Therefore, it is of great significance to carry out the research on the artificial influence of the ionosphere space weather, and the release of ionosphere by chemical substances to the ionosphere is a feasible method to affect the space weather artificially. The ionosphere cavity can affect the propagation of radio waves, high power microwave The efficiency of heating the ionosphere is a series of space activities, and there are many problems to be solved in basic research, such as the plasma instability in the ionospheric hole boundary layer from ion frequency to low hybrid frequency, and the generation and growth of these instability is an examination of the evolution process of the ionosphere cavity. Therefore, the study of the release of ionospheric cavities by chemical substances is a research topic with the frontiers of national defense security and basic plasma physics.
In the past few decades, scientists around the world have carried out a large number of chemical substances actively releasing the ionospheric cavity space experiments and numerical simulation studies. The main means of space active experiment depend on coherent scattering radar, incoherent scattering radar, all day spectrometer, and some ground, rocket and spaceborne equipment. The physical problem of large scale has a great advantage. However, the limitation of the time and space resolution of the equipment and the instability process of the kinetic study scale such as the electronic ion hybrid instability have not been well studied.
We have studied the nonlinear evolution of the active release of chemical substances into the ionospheric hole boundary layer in the laboratory plasma. First, the feasibility of the ionospheric cavity study in the laboratory environment was verified. The air glow discharge is used in this paper because the components and chemical processes of the air glow discharge are close to the real ionospheric environment. The plasma is used to simulate the ionosphere environment. After the formation of the background plasma, we release SF6, CC12F2 and C02 into the plasma to form an simulated ionospheric cavity. The experiment was conducted by microwave interference and spectroscopy to study the evolution of the simulated ionosphere cavity, and the evolution of the density ladder was observed with the evolution of the plasma pressure and release ratio. It is found that the density gradient caused by the release of different chemicals is in accordance with the observational results of the space active experiment. At the same time, we also found that the negative ion intermediate product (NI) material is more effective than the positive ion intermediate (PI) material to reduce the electron density; and the time required for the formation of the ionospheric cavity by the NI substance is shorter than that of the PI. At the same time, we also observed the enhancement of the gas glow of the 630nm resulting from the enhancement of 777.4m's air glow and the release of C02 by the release of SF6, which is in accordance with the results of the whole day spectrograph observation. It is proved that the laboratory plasma has the same process as active space testing, which proves our research side. The feasibility of the law.
On this basis, we have developed a method to study the generation and evolution of ionospheric cavity in laboratory environment, that is, we can produce Omega pe/ Omega CE, beta value and a series of non dimensional parameters that are the same or close to the real space environment in the laboratory by the method of dimensionless parametric calibration. The physical process is the same as space plasma. In the laboratory environment, the physical problems of the ionospheric hole boundary layer can be studied in detail by controlling the experimental parameters. At the same time, the space-time resolution of the laboratory plasma diagnosis is superior to that of the space observation. Therefore, the laboratory environment can be refined by the calibration method. It is necessary to study the microcosmic physics problems of ionospheric void boundary layer evolution.
We have studied the nonlinear evolution process of the ionospheric hole boundary layer by this method, and obtained the evolution process of the plasma electron density and plasma potential in the boundary layer. We observed that there is a huge density gradient Vn. and a f rise in the plasma potential on the boundary layer, and the electron density gradient Vn. in the boundary layer is found. The free energy is provided for the plasma potential fluctuations. Due to the change of F in the plasma suspension potential, the generation of E (R) in the non-uniform electric field will lead to the generation of the shear E x B flow at the boundary layer. The shear flow will drive a series of plasma instability from the ion frequency to the hybrid frequency. We found a low hybrid frequency range internal wave structure in the fluctuation of the suspended potential. Through the cross power spectrum analysis and the bispectrum analysis of the structure, we confirmed that the structure is a shear flow driven electron ion hybrid instability (Electron-Ion Hybrid Instability). The growth of the electron ion hybrid instability in the boundary layer and the formation of the vortex coherent structure play an important role in the nonlinear evolution of the ionospheric cavity. For example, the formation of the irregular body of the boundary layer density is related to the electronic ion hybrid instability. The observation results of space active experiments are of great significance.
We also studied the electromagnetic fluctuations in the ionospheric hole boundary layer. The magnetic probe signals show that there is a strong electromagnetic fluctuation on the boundary layer. The fluctuation has BT, BZ and B theta components, and the component of theta is far greater than that of the other components. Further cross-correlation analysis shows that this is the whistler mode of the right spin polarization. And by comparing the frequency of the electrostatic electron ion hybrid mode to the electromagnetic mode, we judge that the whistler model comes from the nonlinear scattering of the electrostatic electron ion hybrid mode. This is the first time to give the experiment of conversion from the electrostatic frequency to the electromagnetic frequency. Evidence.
In a word, we studied the evolution process of the ionospheric boundary layer formed by chemical active release in the laboratory environment. By using the method of dimensionless parametric calibration, we studied the electrostatic fluctuations and electromagnetic fluctuations in the region, and found the evidence for the existence of the electrostatic electron ion hybrid mode and the whistler mode of its electromagnetic wave band. It is also proved indirectly that the electrostatic ion hybrid mode in the boundary layer can be transformed into an electromagnetic whistle mode through nonlinear scattering. These electrostatic and electromagnetic fluctuations play an important role in the dynamic behavior of the evolution process of the boundary layer. Therefore, it can form a good complementary effect with the two main research methods (space active and numerical simulation) of the current ionospheric cavity, and it can accumulate experience for the country's forthcoming active space experiment.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：P352

【參考文獻】

相關(guān)期刊論文 前1條

1 黃勇;時家明;袁忠才;;Numerical Simulation of Ionospheric Electron Concentration Depletion by Rocket Exhaust[J];Plasma Science and Technology;2011年04期

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本文編號：1997095